1. Field of the Invention
The invention relates to a light emitting diode driving technology, and more particularly, to a light emitting diode driving apparatus and a light emitting diode backlight system using the same.
2. Description of Related Art
Due to rapidly advancing semiconductor technologies in the recent years, portable electronics and flat panel displays have also gained popularity. Among various types of flat display panel, liquid crystal displays (LCDs) have gradually become the mainstream display products due to the advantages such as a low operating voltage, free of harmful radiation, light weight and small and compact size. In general, the LCD is not equipped with a self-luminance function, and thus a backlight module is required to be disposed underneath an LCD panel, so as to supply a light (backlight) source to the LCD panel.
A conventional backlight module can be roughly classified into two types, i.e. a cold cathode fluorescent lamp (CCFL) backlight module and a light emitting diode (LED) backlight module. Since the light emitting diode backlight module is capable of improving color gamut of the LCD, panel manufacturers prefer to employ the light emitting diode backlight module in replacement of the CCFL backlight module.
The light emitting diode backlight module generally includes a plurality of light emitting diode strings connected in parallel, and each light emitting diode string is composed by a plurality of light emitting diodes connected in series. In a conventional light emitting diode backlight system, a light emitting diode driving apparatus is generally composed by circuits such as a control chip, a power switch and a power conversion circuit. The control chip may provide a switching signal to switch the power switch, so that the power conversion circuit may generate a driving signal in response to switching of the power switch to drive the light emitting diode string, so as to turn on the light emitting diode string for emitting light.
Generally, the control chip may adjust the driving signal provided by itself according to various control signals, so as to realize control functions such as adjusting luminance of the backlight module and turning on or off the backlight module. However, to realize above control functions, in the conventional light emitting diode apparatus, the control chip at least require two different complex function pins to respectively receive the control signal for dimming and the control signal for controlling the backlight module to be turned on or off.
In an integrated circuit layout of the control chip with a fixed layout area, difficulty and complexity of circuit layout are relatively higher when a number of the complex function pins increases. In addition, in case of a tight layout space, a possibility that an unexpected coupling phenomenon to occur may also be significantly increased.